linux 下获取当前网络连接状态的两种方法

ZZZZ:  http://blog.csdn.net/suer0101/article/details/8313173

#include <linux/sockios.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/if.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>


#define ETHTOOL_GLINK        0x0000000a /* Get link status (ethtool_value) */


typedef enum { IFSTATUS_UP, IFSTATUS_DOWN, IFSTATUS_ERR } interface_status_t;


typedef signed int u32;


/* for passing single values */
struct ethtool_value
{
    u32    cmd;
    u32    data;
};


interface_status_t interface_detect_beat_ethtool(int fd, char *iface)
{
    struct ifreq ifr;
    struct ethtool_value edata;
   
    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, iface, sizeof(ifr.ifr_name)-1);


    edata.cmd = ETHTOOL_GLINK;
    ifr.ifr_data = (caddr_t) &edata;


    if (ioctl(fd, SIOCETHTOOL, &ifr) == -1)
    {
        perror("ETHTOOL_GLINK failed ");
        return IFSTATUS_ERR;
    }


    return edata.data ? IFSTATUS_UP : IFSTATUS_DOWN;
}


int main (int argc, char *argv[])
{
    FILE *fp;
    interface_status_t status;
    char buf[512] = {'\0'};
    char hw_name[10] = {'\0'};
    char *token = NULL;


    /* 获取网卡名称 */
    if ((fp = fopen("/proc/net/dev", "r")) != NULL)
    {
        while (fgets(buf, sizeof(buf), fp) != NULL)
        {
            if(strstr(buf, "eth") != NULL)
            {       
                token = strtok(buf, ":");
                while (*token == ' ') ++token;
                strncpy(hw_name, token, strlen(token));
            }
        }
    }
    fclose(fp);
//方法一：查看一个文件文件，相对来说比较简单
#if 1
    char carrier_path[512] = {'\0'};
    
    memset(buf, 0, sizeof(buf)); 
    snprintf(carrier_path, sizeof(carrier_path), "/sys/class/net/%s/carrier", hw_name);
    if ((fp = fopen(carrier_path, "r")) != NULL)
    {
        while (fgets(buf, sizeof(buf), fp) != NULL)
        {
            if (buf[0] == '0')
            {
                status = IFSTATUS_DOWN;
            }
            else
            {
                status = IFSTATUS_UP;
            }
        }
    }
    else
    {
        perror("Open carrier ");
    }
    fclose(fp);
#endif


//方法二：用函数吧！有点复杂，但是也是一种有效的办法
#if 1
    int fd;
    
    if((fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        perror("socket ");
        exit(0);
    }
    status = interface_detect_beat_ethtool(fd, hw_name);
    close(fd);
#endif


    switch (status)
    {
        case IFSTATUS_UP:
            printf("%s : link up\n", hw_name);
            break;
        
        case IFSTATUS_DOWN:
            printf("%s : link down\n", hw_name);
            break;
        
        default:
            printf("Detect Error\n");
            break;
    }


    return 0;
}